This invention relates to a rotation device, such as a clutch and a bearing, for disposing between two parts of a mechanism, such as driving and driven parts of a starting motor used for engines of automobiles. This invention also relates to a method of fabricating the rotation device.
A starting motor with a conventional overrunning clutch will hereinafter be described in order to explain the background of the present invention.
FIG. 1 illustrates a starting motor having a typical example of the conventional overrunning clutch, in which an output shaft 3 is operatively connected to a motor body 1 via an overrunning clutch 2. The output shaft 3 has a pinion concentrically and integrally formed with its front end (i.e., the left end in FIG. 1). An electromagnetic unit 4 is connected to the output shaft 3 for reciprocating the output shaft 3 in its axial direction so as to engage and disengage the pinion of the output shaft with and from a ring-shaped gear of an engine.
The overrunning clutch 2 includes: a shaft-like inner race 6 rotatably supported by a frame 12; a hollow cylindrical outer casing 5 rotatably disposed around the inner race 6; a plurality of locking rollers 7 interposed between the outer casing 5 and the inner race 6; and an annular sealing plate 8 rotatably disposed around the inner race 6 and fixed to the outer casing 5. As shown in FIG. 2, the outer casing 5 has a plurality of chambers 13 formed in it, at equal angular intervals. Each of these chambers 13 opens to a rear end face 16 of the outer casing 5. Reference numeral 14 denotes coil springs for pressing the locking rollers 7. The locking rollers 7 are received in the respective chambers 13 for drivingly connecting and disconnecting the outer casing 5 to and from the inner race 6. More specifically, upon the rotation of the outer casing 5 in one direction, the locking rollers 7 connects the outer casing 5 to the inner race 6, and upon the rotation of the inner race 6 in the same direction, the locking rollers 7 disconnects the inner race 6 from the outer casing 5. Grease as a lubricating agent is filled within the chambers 13. The sealing plate 8 is provided for aligning the axes of the outer casing 5 and inner race 6 and also for closing the openings of the chambers 13 so as to prevent the leakage of the grease out of the chambers 13.
The outer casing 5 has a driven gear formed therearound thereby being drivingly connected to the motor body 1. On the other hand, the inner race 6 is splined to the output shaft 3. That is to say, the clutch 2 is adapted to transfer torque from the motor body 1 to the output shaft 3 but not from the output shaft 3 to the motor body 1.
With the aforementioned starting motor which employs the overrunning clutch 2, it is enabled to rotate the ring-shaped gear of the engine so that the engine is started. Also, it is enabled, with this starting motor, to prevent the motor body 1 from being subjected to unnecessary torque during the operation of the engine.
In order to assure the smooth connecting and disconnecting actions of the locking rollers 7, the overrunning clutch 2 is required to have the following conditions:
(1) The axis of the outer casing 5 is accurately aligned with that of the inner race 6. PA0 (2) The openings of the chambers 13 are completely closed so that the grease does not leak out of the chambers 13. PA0 (3) The sealing plate 8 is firmly fixed to the outer casing 5.
In the above-mentioned clutch 2, the inner face of the sealing plate 8 serves as a part of the supporting surface which is slidably in contact with the inner race 6. From this perspective, how the sealing plate 8 is fixed to the outer casing 5 is one of the fundamental elements in determining whether or not the above-mentioned conditions are satisfied. In other words, an improvement of the fixing technique for the sealing plate may result in enhancement of the quality of the clutch 2.
As to the clutch shown in FIG. 1, the sealing plate 8 is in direct contact with the rear end face 16 of the outer casing 5 and also fits in an annular extension 15 which is formed on the periphery of the rear end face 16 of the outer casing 5. The periphery of this sealing plate 8 is caulked by means of a tool such as a caulking chisel so that the sealing plate is firmly fixed to the annular extension 15. Furthermore, a snap ring 9 fits in the annular extension to serve as a stopper for the sealing plate 8.
Although in this clutch 2, the axis of the outer casing is aligned with that of the inner race 6 with satisfactory accuracy, there arises problems with the fixing strength and the sealing property of the sealing plate 8 not being satisfactory.
Japanese Patent Publication No. sho 57-37775 discloses a prior art clutch, which may solve the above-mentioned problems. As shown in FIG. 3, the disclosed outer casing 5 has an annular extension 15 having a projecting height not less than the thickness of the sealing plate and also having an inwardly opening groove 10 circumferentially formed in the annular extension 15. A part of the periphery of the sealing plate 8 protrudes into the groove 10 by being plastically deformed, and thus the sealing plate 8 is attached to the outer casing 5. More specifically, the groove 10 is formed at such a position that the distance between the rear end face 16 of the outer casing 5 and the groove 10 is smaller than the thickness of the sealing plate 8. The sealing plate 8 is pressed by a pressing machine so that the periphery of the sealing plate 8 is deformed.
According to this prior art, the sealing plate 8 may be firmly secured to the outer casing 5, and also close the openings of the chambers 13. However, even with such a clutch, the following problems arise.
Since the periphery of the sealing plate 8 is deformed to form a protrusion into the groove 10 by the pressing operation, that is, since the sealing plate 8 is extended in a radially outward direction perpendicular to the direction in which the pressing force is applied, a large pressing machine which is capable of applying a substantially large pressing force is required. Moreover, the large pressing force may result in unnecessary deformation of the inner portion of the sealing plate 8, which may lower the accuracy with which the axis of the outer casing 5 is aligned with that of the inner race 6.